drm/radeon: removed optional dummy encoder mode_fixup function.

mode_fixup function for encoder drivers became optional with patch
http://patchwork.freedesktop.org/patch/msgid/1455106522-32307-1-git-send-email-palminha@synopsys.com

This patch set nukes all the dummy mode_fixup implementations.

(made on top of Daniel topic/drm-misc branch)
Signed-off-by: NCarlos Palminha <palminha@synopsys.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1b99680b8cf81977597dec5daedff9b684d3ed19.1455540137.git.palminha@synopsys.com

drivers/gpu/drm/radeon/atombios_encoders.c

@@ -2623,16 +2623,8 @@ radeon_atom_ext_dpms(struct drm_encoder *encoder, int mode)
 
 }
 
-static bool radeon_atom_ext_mode_fixup(struct drm_encoder *encoder,
-				       const struct drm_display_mode *mode,
-				       struct drm_display_mode *adjusted_mode)
-{
-	return true;
-}
-
 static const struct drm_encoder_helper_funcs radeon_atom_ext_helper_funcs = {
 	.dpms = radeon_atom_ext_dpms,
-	.mode_fixup = radeon_atom_ext_mode_fixup,
 	.prepare = radeon_atom_ext_prepare,
 	.mode_set = radeon_atom_ext_mode_set,
 	.commit = radeon_atom_ext_commit,